The heating step for food processing is one of the important processes for inducing quality changes in an object and determining the nature thereof, regardless of the type or purpose of the object. A variety of heating methods are known, and these are classified into external heating (direct heating and indirect heating) and internal heating (self-heating). Typical examples of the internal heating system are Joule heating, microwave heating, and high-frequency heating.
Joule heating is used, for instance, for the purpose of disinfection and endogenous enzyme deactivation and the like for fluid foods, such as juices, sauces, ketchup, and mayonnaise (Patent Documents 1 to 4, and the like). A technology for production of meat-paste products has been disclosed whereby after preheating by Joule heating, the product is molded and then the molded product is further subjected to Joule heating (Patent Document 5). Moreover, when producing fish-paste products such as chikuwa, satsuma-age, or crab-flavored kamaboko, Joule heating is used to heat the fish paste after molding or Joule heating is used for preheating of the fish paste before molding (Patent Documents 6 to 9, and the like).
Microwave heating is widely used for a microwave oven. Patent Documents 10 and 11 disclose a method for heating/molding a skinless paste product using microwave heating.
High-frequency heating is a heating system based on the same theory as microwave heating, but uses an electromagnetic wave of a smaller frequency than microwaves.
Examples of sausages known as a processed mincemeat product include a fish sausage obtained by mixing a fish meat paste and secondary raw materials, filling the mixture in a casing, and heating, and a livestock meat sausage obtained by filling a meat paste in an edible casing made from sheep intestine, and the like, smoking, and heating before eating. These are foods that are molded in casings and then heated.